Balance indicator



A ril 12, 1927. 1,624,484

R. D. EVANS BALANCE INDICATOR Filed Sept. 19, 1922 VAR/118i CUfiRs/vr 2 GENERIfOR WITNESSES: INVENTOR v ATTORNEY Patented Apr. 12, 1927.

UNITED STATES PATENT QFFICE.

ROBERT D. EVANS, OF WILKINSBURG, PENNSYLVANIJZL, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A COEPORATIOI OF PENNSYLVANIA.

BALANCE INDICATOR.

Application filed September 19, 1922. Serial No. 589,2?1.

My invention relates to indicating means and particularly to means torindicating unbalanced conditions of telephone and power circuits.

The object of my invention is to provide a simple and effective means for readily detecting unbalance in electrical circuits and particularly in telephone circuits where inductive interference and other influences render the lines noisy.

In telephone and other communication circuits, the system is considered balanced when the two sides of a circuit have equal linear impedance and equal shunt admittance to ground. This balance may be disturbed by contact of the conductors with trees and other grounded objects, as well as by other factors. If a potential be applied to an unbalanced circuit, unbalance currents will beproduced.

A balanced communication circuit will be unaffected by the inductive interference of a power circuit. However, an unbalanced power circuit will produce additional losses in an unbalanced telephone circuit.

If balanced Voltages are applied to an unbalanced power circuit, some current may be caused to flow in the earth. Under such conditions, since there is a relatively great distance between the outgoing and the return currents, the efl'ect on adjacent communication circuits will be relatively greater.

Unbalance causes noise in the telephone apparatus and renders conversation diflicult, if not impossible.

The condition of unbalance may readily be corrected, if the same beknown, but, to the best of my knowledge, no device so simple and effective as the one herein proposed has heretofore been suggested for determining unbalance.

In practicing my invention, I provide means whereby a section of the circuit under test may be included in a static network. which is normally balanced under balanced conditions in the circuit, and means connected to the network for determining unbalance by a comparison of noises.

The single :[igure of the accompanying drawing is a diagrammatic view of a device embodying my invention, together with the circuit connections therefor.

The device comprises, in general, a telephone receiver 1, a standard tone generator 2, a resistor 3 for varying the magnitude of the current generator by the device 2, impedance devices t and 5 that are connected to a circuit 6 to be tested and a double-throw, three-pole switch 7. The generator 2 ge'neu ates an alternating or pulsating current at audible frcquencyefor instance, 800 cycles.

The impedance devices a and 5, preferably resistors, are connected across the conductors of the circuit 6 at a predetermined distant-e from each other. The resistor 5 is connected from its midpoint to ground through a conductor 8. The resistor 4: is adapted to be connected, in one position ofthe switch 7, from its midpoint to ground, through a conductor 9, through one pole 10 of the switch 7, a conductor 11, the standard tone generator 2 and a conductor 12.

The receiver 1 is adapted to be connected, in one position of the switch 7, to the conductors of the circuit 6, through conductors 14, poles 15 and 16 of the switch 7 and conductors 17 In the other position of the switch 7, the receiver 1 and the generator 2 are connected through the resistor 3.

With the above-described arrangement, when the circuit 6 is balanced, there will be no current flow in the conductors 17 and, consequently, there will be no effect on the receiver 1 when the switch 7 is closed in its upper position.

However, under unbalanced conditions, a current will flow in the conductors 17 and a tone corresponding to the current generated by the device 2 will be heard in the receiver 1. The degree of unbalance will determine the distinctness of the sound heard in the receiver 1. This sound may be directly compared with the sound in the same pitch but of known magnitude by moving the switch 7 to its lower closed position. The magnitude of the sound used for comparison is adjusted by means of the variable resistor This resistor is suitably calibratcd so that when the sounds heard in the receiver 1 for both positions of the switch are equal, an indication is pro- \ided of the degree of unbalance of the telephone line 6.

Since the pitch of the sounds heard in both the upper and lower positions of the switch 7 will be the same, the strength or distinctness of the sounds may be readily compared. Hence, the magnitude of the fault may be determined and corrected accordingly.

My invention may be modified my employing ditlerent values of the impedance 5. For instance, this in'ipedance may be proportioned to represent a circuit of infinite length. The impedance may approach infinite *alues, in which case the effect of capacity unbalance oi the circuit 6 would be ind"'ated more clearly. Also, the in1- pedance may approach zero value, in which case the etl'ect of series unbalance oi the condoctors would be indicated more clearly.

\Vhile I have shown and described a particular form of my invention, changes and modifications may be made therein without departing from the spirit and scope thereof, as sett'orth in the appended claims.

I claim as my invention:

1. In a device for detecting unbalance in an electric circuit, the combination with a variable-circuit generator having one terminal connected to ground, of a variable resistor, a pair of impedance devices c0n nected across the conductors of said circuit, one of said inn mdance devices being grounded at the mid point thereof. a telephone receiver, and switching: means for connecting the receiver to the generatorthrough said resistor and for connecting the receiver across the conductors of said circuit between the impedance devices and con necting the other terminal of the generator to the mid point of the other impedance device.

2. In combinzu ion, a variableciirrent generator, an indicating device, a circuit, an impedance bridged across said circuit, and means for connecting said generator to the midpoint of said impedance and said device to said circuit. said means also pern'iitting the independent connection of said device to said generator through a local circuit of variable resistance.

In testimony whereof, I have hereunto subscribed my name this 15th day of September, 1922.

ROBERT D. EVANS.

CERTIFICATE OF commoner-4.

Patent No. 1,624,484. Grantefi Apri; 12, 1927, to

ROBERT D. EVANS,

It is hereby certified that error agpears in the printed specification of the above numbered patent requiring correction as foiiows: iage 2, line 23, claim ,1. for $116 tompound Word "vatiablewirouit" read "variable-current"; and that the said Letters Patent should be reafiwith this eorreotioa: therein that the same may conform to the record of the case the Patent Qffice.

Signed and sealed this 17th day of May, A. F). 1927.

I41, J 4 Moore,

Seal. Aeting Commissioner of Patents, 

